The present disclosure relates to a gas turbine engine and, more particularly, to a bleed air cavity heat shield arrangement for a gas turbine engine.
Gas turbine engines, such as those that power modern commercial and military aircraft, generally include a compressor section to pressurize an airflow, a combustor section to burn a hydrocarbon fuel in the presence of the pressurized air, and a turbine section to extract energy from the resultant combustion gases.
Heat shields are used in various engine sections such as within the compressor section to isolate Outer Air Seal (OAS) and case flanges to control thermal response. This facilitates control of rotor blade tip clearances with respect to a rub strip of the OAS. Tighter tip clearance improves engine efficiency and performance.
The heat shields generally span the entire circumference of each or a multiple of engine stages and are usually split into multiple, typically about one-hundred eighty (180) degree segments. A gap between the heat shield segments facilitates engine assembly and accommodates circumferential thermal growth. The size of this gap is generally determined by the relationship between the thermal growth of the heat shield segments and the OAS/case flanges at each bolt location. The gap is sized such that even under maximum tolerance and thermal effects, the heat shield segment ends do not touch. Bleed air leakage through the circumferential thermal expansion gap, however, need also to be limited to isolate the flanges from bleed cavity air. To minimize the bleed air leakage, a cover plate spans the circumferential thermal expansion gap to form a single lap joint.
To accommodate axial thermal growth and tolerances, heat shield retainers provide either a relatively loose or a relatively tight heat shield axial interface. In a relatively loose configuration, the relatively loose interface may result in vibration which may cause wear on adjacent components such as the OAS and case flanges. In a relatively tight configuration, the relatively tight interface may result in deformation that yields the heat shield segments. The cover plates also may lift during assembly due to the deformation such that sealing benefits of the covers are reduced.